Write the following as an expression, "15 added to the product of 7 and c"​

Ineed with number 17 i don’t get it at alll

Which sum or difference identity would you use to verify that cos (180° - ∅) = -cos ∅? a. sin (α -β) = sin α cos β – cos α sin β b. cos (α -β) = cos α cos β – sin α sin β c. cos (α -β) = cos α cos β + sin α sin β d. sin (α + β) = sin α cos β + cos α sin β

Find the nonpermissible replacement for binthis expression.b2/5b +5